/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at:
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package io.netty.example.http2.helloworld.server;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.http.HttpServerUpgradeHandler;
import io.netty.handler.codec.http2.DefaultHttp2Headers;
import io.netty.handler.codec.http2.Http2ConnectionDecoder;
import io.netty.handler.codec.http2.Http2ConnectionEncoder;
import io.netty.handler.codec.http2.Http2ConnectionHandler;
import io.netty.handler.codec.http2.Http2Exception;
import io.netty.handler.codec.http2.Http2Flags;
import io.netty.handler.codec.http2.Http2FrameListener;
import io.netty.handler.codec.http2.Http2Headers;
import io.netty.handler.codec.http2.Http2Settings;
import io.netty.util.AsciiString;
import io.netty.util.CharsetUtil;

import static io.netty.buffer.Unpooled.copiedBuffer;
import static io.netty.buffer.Unpooled.unreleasableBuffer;
import static io.netty.example.http2.Http2ExampleUtil.UPGRADE_RESPONSE_HEADER;
import static io.netty.handler.codec.http.HttpResponseStatus.OK;

/**
 * A simple handler that responds with the message "Hello World!".
 */
public final class HelloWorldHttp2Handler extends Http2ConnectionHandler
        implements Http2FrameListener
{

    static final ByteBuf RESPONSE_BYTES = unreleasableBuffer(
            copiedBuffer("Hello World", CharsetUtil.UTF_8));

    HelloWorldHttp2Handler(Http2ConnectionDecoder decoder,
            Http2ConnectionEncoder encoder, Http2Settings initialSettings)
    {
        super(decoder, encoder, initialSettings);
    }

    /**
     * Handles the cleartext HTTP upgrade event. If an upgrade occurred, sends a
     * simple response via HTTP/2 on stream 1 (the stream specifically reserved
     * for cleartext HTTP upgrade).
     */
    @Override
    public void userEventTriggered(ChannelHandlerContext ctx, Object evt)
            throws Exception
    {
        if (evt instanceof HttpServerUpgradeHandler.UpgradeEvent)
        {
            // Write an HTTP/2 response to the upgrade request
            Http2Headers headers = new DefaultHttp2Headers()
                    .status(OK.codeAsText())
                    .set(new AsciiString(UPGRADE_RESPONSE_HEADER),
                            new AsciiString("true"));
            encoder().writeHeaders(ctx, 1, headers, 0, true, ctx.newPromise());
        }
        super.userEventTriggered(ctx, evt);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
            throws Exception
    {
        super.exceptionCaught(ctx, cause);
        cause.printStackTrace();
        ctx.close();
    }

    /**
     * Sends a "Hello World" DATA frame to the client.
     */
    private void sendResponse(ChannelHandlerContext ctx, int streamId,
            ByteBuf payload)
    {
        // Send a frame for the response status
        Http2Headers headers = new DefaultHttp2Headers()
                .status(OK.codeAsText());
        encoder().writeHeaders(ctx, streamId, headers, 0, false,
                ctx.newPromise());
        encoder().writeData(ctx, streamId, payload, 0, true, ctx.newPromise());
        try
        {
            flush(ctx);
        }
        catch (Throwable cause)
        {
            onError(ctx, cause);
        }
    }

    @Override
    public int onDataRead(ChannelHandlerContext ctx, int streamId, ByteBuf data,
            int padding, boolean endOfStream)
    {
        int processed = data.readableBytes() + padding;
        if (endOfStream)
        {
            sendResponse(ctx, streamId, data.retain());
        }
        return processed;
    }

    @Override
    public void onHeadersRead(ChannelHandlerContext ctx, int streamId,
            Http2Headers headers, int padding, boolean endOfStream)
    {
        if (endOfStream)
        {
            ByteBuf content = ctx.alloc().buffer();
            content.writeBytes(RESPONSE_BYTES.duplicate());
            ByteBufUtil.writeAscii(content, " - via HTTP/2");
            sendResponse(ctx, streamId, content);
        }
    }

    @Override
    public void onHeadersRead(ChannelHandlerContext ctx, int streamId,
            Http2Headers headers, int streamDependency, short weight,
            boolean exclusive, int padding, boolean endOfStream)
    {
        onHeadersRead(ctx, streamId, headers, padding, endOfStream);
    }

    @Override
    public void onPriorityRead(ChannelHandlerContext ctx, int streamId,
            int streamDependency, short weight, boolean exclusive)
    {
    }

    @Override
    public void onRstStreamRead(ChannelHandlerContext ctx, int streamId,
            long errorCode)
    {
    }

    @Override
    public void onSettingsAckRead(ChannelHandlerContext ctx)
    {
    }

    @Override
    public void onSettingsRead(ChannelHandlerContext ctx,
            Http2Settings settings)
    {
    }

    @Override
    public void onPingRead(ChannelHandlerContext ctx, ByteBuf data)
    {
    }

    @Override
    public void onPingAckRead(ChannelHandlerContext ctx, ByteBuf data)
    {
    }

    @Override
    public void onPushPromiseRead(ChannelHandlerContext ctx, int streamId,
            int promisedStreamId, Http2Headers headers, int padding)
    {
    }

    @Override
    public void onGoAwayRead(ChannelHandlerContext ctx, int lastStreamId,
            long errorCode, ByteBuf debugData)
    {
    }

    @Override
    public void onWindowUpdateRead(ChannelHandlerContext ctx, int streamId,
            int windowSizeIncrement)
    {
    }

    @Override
    public void onUnknownFrame(ChannelHandlerContext ctx, byte frameType,
            int streamId, Http2Flags flags, ByteBuf payload)
    {
    }
}
